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Everyday Ideas–Pee Theory

February 26, 2014

One of the powerful ideas we’ve had in inquiry class this semester is called “Amy’s Pee Theory”. It’s an idea we’ve returned to again and again in explaining phenomena. Amy’s pee theory states that if you pee a normal size amount in a very large pool, no one will notice. The pee (to be sure) is still there, but it’s been spread out over such a large thing, that it’s not concentrated enough to have a noticeable effect. Peeing in a smaller container of water, such as a toilet, results in a more obvious effect (yellow color), because the pee is concentrated in a small container. This idea is our class’s instantiation of beginning to think about a thermal reservoir.

Last week, our class discussed the energy tracking of a battery-powered fan. We spent most of our time trying to decide whether the room’s thermal energy increases, decreases, or stays the same. We touched upon lots of everyday experience–running the thermostat in your house switched to “A/C”, “Heat”, or just “Fan”; actual temperature vs. “feels” like due to wind chill, fanning to “cool yourself” off, you don’t seem to cool down the room; how the moment you stop fanning, the cool feel goes away; how ridiculous it seems that you could really cool off a room by having lots of people fanning, vents in your car, etc.

Eventually, people were convinced that fanning didn’t actually reduce the temperature, but we didn’t have an explanation for why you felt cooler. The idea that was eventually was proposed was, “Fanning helps the thermal energy you’ve produced around you go away, by blowing the warm air away from you.” Several said that there mind was blown at hearing that idea.

Eventually,everyone agreed a room should technically get hotter, but you wouldn’t be able to tell via “Amy’s pee theory.” The room is so big that the little bit of thermal energy put off by the motor wouldn’t make a big difference. This nicely motivated why we should try the experiment with a fan in a very small “room”. So we ran a fan inside a small cooler for 10 minutes while we went outside to make moon observations, and the temperature inside the cooler had risen by 12 degrees. Pretty cool. Upon opening the cooler, pretty soon the cooler was back to being normal temperature, because the “pee” that we had kept trapped in a toilet had now spread out into the pool. The room was not measurably hotter as a result.

After the experiment, someone blurted out remembering a long time when their house had been flooded. To dry out the house, they had to bring in dozens of industrial fans, and they recalled how freakin’ hot it made the house. Bringing in dozens of huge fans was like getting several bus full of kids to pee in the pool.